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mm: extended batches for generic mmu_gather
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Instead of using a single batch (the small on-stack, or an allocated
page), try and extend the batch every time it runs out and only flush once
either the extend fails or we're done.

Signed-off-by: Peter Zijlstra <[email protected]>
Requested-by: Nick Piggin <[email protected]>
Reviewed-by: KAMEZAWA Hiroyuki <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: David Miller <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Russell King <[email protected]>
Cc: Paul Mundt <[email protected]>
Cc: Jeff Dike <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Namhyung Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Peter Zijlstra authored and torvalds committed May 25, 2011
1 parent 2672391 commit e303297
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Showing 2 changed files with 84 additions and 47 deletions.
129 changes: 83 additions & 46 deletions include/asm-generic/tlb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,16 +19,6 @@
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

/*
* For UP we don't need to worry about TLB flush
* and page free order so much..
*/
#ifdef CONFIG_SMP
#define tlb_fast_mode(tlb) ((tlb)->nr == ~0U)
#else
#define tlb_fast_mode(tlb) 1
#endif

#ifdef CONFIG_HAVE_RCU_TABLE_FREE
/*
* Semi RCU freeing of the page directories.
Expand Down Expand Up @@ -78,6 +68,16 @@ extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
*/
#define MMU_GATHER_BUNDLE 8

struct mmu_gather_batch {
struct mmu_gather_batch *next;
unsigned int nr;
unsigned int max;
struct page *pages[0];
};

#define MAX_GATHER_BATCH \
((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))

/* struct mmu_gather is an opaque type used by the mm code for passing around
* any data needed by arch specific code for tlb_remove_page.
*/
Expand All @@ -86,22 +86,48 @@ struct mmu_gather {
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
struct mmu_table_batch *batch;
#endif
unsigned int nr; /* set to ~0U means fast mode */
unsigned int max; /* nr < max */
unsigned int need_flush;/* Really unmapped some ptes? */
unsigned int fullmm; /* non-zero means full mm flush */
struct page **pages;
struct page *local[MMU_GATHER_BUNDLE];
unsigned int need_flush : 1, /* Did free PTEs */
fast_mode : 1; /* No batching */

unsigned int fullmm;

struct mmu_gather_batch *active;
struct mmu_gather_batch local;
struct page *__pages[MMU_GATHER_BUNDLE];
};

static inline void __tlb_alloc_page(struct mmu_gather *tlb)
/*
* For UP we don't need to worry about TLB flush
* and page free order so much..
*/
#ifdef CONFIG_SMP
#define tlb_fast_mode(tlb) (tlb->fast_mode)
#else
#define tlb_fast_mode(tlb) 1
#endif

static inline int tlb_next_batch(struct mmu_gather *tlb)
{
unsigned long addr = __get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
struct mmu_gather_batch *batch;

if (addr) {
tlb->pages = (void *)addr;
tlb->max = PAGE_SIZE / sizeof(struct page *);
batch = tlb->active;
if (batch->next) {
tlb->active = batch->next;
return 1;
}

batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
if (!batch)
return 0;

batch->next = NULL;
batch->nr = 0;
batch->max = MAX_GATHER_BATCH;

tlb->active->next = batch;
tlb->active = batch;

return 1;
}

/* tlb_gather_mmu
Expand All @@ -114,16 +140,13 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
{
tlb->mm = mm;

tlb->max = ARRAY_SIZE(tlb->local);
tlb->pages = tlb->local;

if (num_online_cpus() > 1) {
tlb->nr = 0;
__tlb_alloc_page(tlb);
} else /* Use fast mode if only one CPU is online */
tlb->nr = ~0U;

tlb->fullmm = fullmm;
tlb->fullmm = fullmm;
tlb->need_flush = 0;
tlb->fast_mode = (num_possible_cpus() == 1);
tlb->local.next = NULL;
tlb->local.nr = 0;
tlb->local.max = ARRAY_SIZE(tlb->__pages);
tlb->active = &tlb->local;

#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb->batch = NULL;
Expand All @@ -133,24 +156,24 @@ tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
static inline void
tlb_flush_mmu(struct mmu_gather *tlb)
{
struct mmu_gather_batch *batch;

if (!tlb->need_flush)
return;
tlb->need_flush = 0;
tlb_flush(tlb);
#ifdef CONFIG_HAVE_RCU_TABLE_FREE
tlb_table_flush(tlb);
#endif
if (!tlb_fast_mode(tlb)) {
free_pages_and_swap_cache(tlb->pages, tlb->nr);
tlb->nr = 0;
/*
* If we are using the local on-stack array of pages for MMU
* gather, try allocating an off-stack array again as we have
* recently freed pages.
*/
if (tlb->pages == tlb->local)
__tlb_alloc_page(tlb);

if (tlb_fast_mode(tlb))
return;

for (batch = &tlb->local; batch; batch = batch->next) {
free_pages_and_swap_cache(batch->pages, batch->nr);
batch->nr = 0;
}
tlb->active = &tlb->local;
}

/* tlb_finish_mmu
Expand All @@ -160,13 +183,18 @@ tlb_flush_mmu(struct mmu_gather *tlb)
static inline void
tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
{
struct mmu_gather_batch *batch, *next;

tlb_flush_mmu(tlb);

/* keep the page table cache within bounds */
check_pgt_cache();

if (tlb->pages != tlb->local)
free_pages((unsigned long)tlb->pages, 0);
for (batch = tlb->local.next; batch; batch = next) {
next = batch->next;
free_pages((unsigned long)batch, 0);
}
tlb->local.next = NULL;
}

/* __tlb_remove_page
Expand All @@ -177,15 +205,24 @@ tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
*/
static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
{
struct mmu_gather_batch *batch;

tlb->need_flush = 1;

if (tlb_fast_mode(tlb)) {
free_page_and_swap_cache(page);
return 1; /* avoid calling tlb_flush_mmu() */
}
tlb->pages[tlb->nr++] = page;
VM_BUG_ON(tlb->nr > tlb->max);

return tlb->max - tlb->nr;
batch = tlb->active;
batch->pages[batch->nr++] = page;
VM_BUG_ON(batch->nr > batch->max);
if (batch->nr == batch->max) {
if (!tlb_next_batch(tlb))
return 0;
}

return batch->max - batch->nr;
}

/* tlb_remove_page
Expand Down
2 changes: 1 addition & 1 deletion mm/memory.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -994,8 +994,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
spinlock_t *ptl;
int rss[NR_MM_COUNTERS];

init_rss_vec(rss);
again:
init_rss_vec(rss);
pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
arch_enter_lazy_mmu_mode();
do {
Expand Down

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